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WGO Handbook on Diet and the Gut_2016_Final

World Digestive Health Day
WDHD – May 29, 2016
CARBOHYDRATE INTOLERANCE (LACTOSE, SUCROSE AND
FRUCTOSE): IDENTIFICATION AND TREATMENT, continued
DIAGNOSIS
In clinically suspected patients, diagnosis is made on small
intestinal biopsy, which was gold standard for years. Criteria
applied to make the diagnosis include normal small bowel
morphology in the presence of absent or markedly reduced
sucrase activity, isomaltase activity varying from 0 to full
activity, reduced maltase activity, and normal lactase activity,
or in the setting of reduced lactase, a sucrase:lactase ratio of
&lt;1.0.
Molecular genetics helps in making early diagnosis and
avoids invasive, repetitive procedures. At least 80% of
patients have one of four common mutations, namely
p.Val577Gly, p.Gly1073Asp, and p.Phe1745Cys in the sucrase
domain and p.Arg1124X in the isomaltase domain.12 It has
replaced the need for small intestinal biopsy for diagnosis.
TREATMENT
The sucrase-isomaltase intolerance is treated mainly by the
dietary restriction. (See Table 3) Oral supplementation of sucrosidase
(derived from Saccharomyces cerevisiae) can also
be used, if available.
FRUCTOSE INTOLERANCE
Fructose is a monosaccharide, which is naturally present in
fruits and vegetables.13 Fructose, because of its sweet taste,
is used extensively in food industry as a sweetener such as
in juices, candies, and beverages. Fructose is also a constituent
of disaccharides sucrose along with glucose.
HEREDITARY FRUCTOSURIA
Hereditary fructosuria is a rare clinical disease, which occurs
due to a deficiency of this aldolase B enzyme. The deficiency
of enzyme leads to incomplete metabolism of fructose, which
leads to accumulation of fructose-1-phosphate in the liver,
kidney, and intestine. Patients may have symptoms in the
form of hypoglycemia, abdominal pain, vomiting, and diarrhea.
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FRUCTOSE INTOLERANCE
Fructose is generally absorbed passively along with glucose
via GLUT-2 transporter present on the basolateral membrane
of enterocytes. Fructose is also absorbed by GLUT-5 is non
glucose dependent transporter located in the brush border of
the small intestine. Defects in these transporters can lead to
fructose malabsorption. Transportation of ingested glucose
Table 3: Food items, which are restricted and allowed in patients having
sucrose-isomaltose intolerance
Foods to avoid Food items which are allowed
Apple, apricot, banana,
cantaloupe, grapefruit,
melon, mango, orange,
peach, pineapple, and
tangerine
Carrot and potato
Beans, chickpeas, green
peas, lentils, peas, and soy
Yogurt sweetened with
sucrose, sweetened
condensed milk, and
sweetened cream
Sugar (sucrose), ice cream,
all desserts made with
sugar, marmalade, candies,
jellies, chocolate, and
licorice
Commercial cookies and
cakes with added sugar,
sweetened drinks
Wheat, rice, corn, einkorn, oats,
kamut, spelt, rye, bread, pasta,
flour, and cereals with no
added sugar
Avocado, berries, cherries,
fig, grapes, kiwi, lemon,
lime, olives, papaya, pear,
pomegranate, prunes, and
strawberries
All vegetables
Milk, dairy product, butter,
cream, cheeses, and yogurt
sweetened with dextrose or
fructose
All meat, fish, and eggs
All fats
Fructose, honey, cocoa,
unsweetened juice, homemade
low-sucrose cookies, and cakes
through SGLT-1 activates GLUT-2 which in turn gets inserted
on the apical membrane. Therefore, ingestion of glucose enhances
absorption of fructose as well. Glucose also increases
paracellular absorption of fructose. These mechanisms explain
the possible fructose malabsorption after eating foods
whose fructose component is in excess of glucose. Fructose
intolerance can also occur because of diffuse mucosal diseases
of intestine such as celiac disease.
Clinical features are similar to symptoms caused by other
carbohydrates intolerances such as lactose intolerance, as
described above.
The diagnosis of fructose malabsorption can be made by hydrogen
breath test after ingestion of fructose 0.5 gm/kg (maximum
25 gm) dissolved in water. The diagnosis is confirmed by
an increase of &gt;20 ppm in hydrogen or &gt;10 ppm in methane
levels over the baseline twice in succession and abdominal
discomfort after the consumption of the test dose. Fructosehydrogen
test has both sensitivity and specificity of over 80%.
World Digestive Health Day WDHD May 29, 2016 WGO Handbook on DIET AND THE GUT 23